JP2509175B2 - Manufacturing method of wiring structure - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a wiring structure using a polymer resin as an interlayer insulating film or a protective film and a method for manufacturing the same, and more particularly to a substrate and wiring or electrical connection between wirings. An object is to provide a good wiring structure and a manufacturing method thereof.

[Background of the Invention]

Problems of the prior art will be described with reference to FIG. This conventional technology is described in Saiki et al .; IEICE Transactions; Vol 63
-C (9) (1980/9) p586. First second
As shown in FIG. 3A, a polymer resin layer 11 made of polyimide resin is formed on a substrate 10 such as a Si wafer having an insulating layer or wiring layer (not shown) formed on the surface thereof. Next, a mask 12 made of photoresist or the like for forming the connection port 13 is formed, and the connection port 13 is formed using a hydrazine hydrate-based etching solution. On the surface of the substrate 10 exposed by the formation of the connection port 13, a reaction layer 14 is generally formed of an etching liquid or water used for subsequent cleaning and a substance exposed on the surface. For example, Si on the surface of substrate 10
When is exposed, SiO ₂ or the like is generated, and when Al or the like is exposed, Al ₂ O ₃ , Al (OH) _3, or the like is generated. In many cases, the reaction layer 14 has a high resistance or an insulating property, and even if a wiring layer is immediately formed on the reaction layer 14, the wiring layer and the underlying substrate 10 or a wiring layer (not shown) have good electrical properties. Getting a connection is difficult. Therefore, it is necessary to remove this reaction layer 14. The reaction layer 14 can be removed by cleaning with a sputter. As shown in FIG. 2 (b), after removing the mask 12, the entire surface of the substrate 10 is etched with an inert gas ion such as Ar to slightly remove the surface of the polymer resin layer 11 (thickness). 2 to 50 nm) and simultaneously remove the reaction layer 14, and then form a wiring layer 15 without exposing the substrate 10 to the atmosphere as shown in FIG. To process. By using the sputter cleaning as described above, the contact resistance between the wiring layer (not shown) on the surface of the substrate 10 and the wiring layer 15 via the connection port 13 can be obtained without heat treatment. Almost 1 × 10 ^-8
A sufficiently low resistance value of Ω · cm ² was obtained. However, as a result of the study by the present inventor, it was found that the above technique has the following drawbacks. That is, in the above method, when the ratio of the depth T of the connection port 13 to the narrower width W, that is, the aspect ratio is smaller than 1/2, a good connection can be obtained as described above. However, when the aspect ratio exceeds 1/2, as shown in FIG. 2 (d), the reaction layer 14 at the bottom of the connection port 13 is not sufficiently removed by the sputter cleaning, and conversely the polymer resin layer. 11 When a substance that has been etched from the surface is deposited, or when the redeposited layer 16 formed by reacting with the substance exposed at the bottom of the connection port 13 is formed instead, low contact resistance cannot be realized. I knew there was. This is because the incidence of inert gas ions decreases as the aspect ratio of the connection port 13 increases, and the removal rate of the reaction layer 14 decreases, but the substance etched from the surface of the polymer resin layer 11 is the bottom of the connection port 13. It is understood that the redeposited material layer is formed by depositing on the substrate or by decomposition of the material to be etched to generate oxygen and the like, which reacts with the material exposed at the bottom of the connection hole 13. It was Therefore, it was difficult to use the connection port 13 having an aspect ratio of 1/2 or more in the conventional technique. For example, when the thickness of the polymer resin layer 11 is 1 μm, it is difficult to use the fine connection port 23 having the width W of 2 μm or less.

[Object of the Invention]

It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and to provide a wiring structure capable of using a connection port having a high aspect ratio of 1/2 or more, and more preferably 1 or more, and a manufacturing method thereof. To do.

[Outline of Invention]

The cause of the drawbacks of the prior art is that the redeposited material layer 16 is formed as shown in FIG. 2 (d) during the sputter cleaning. As a result of a detailed study, it was found that such a reattachment layer 16 is particularly likely to be formed when the connection port 13 is formed in the polymer resin layer. On the other hand
It has been found that when formed in a layer made of SiO ₂ or metal, a redeposited layer is hardly formed even if the spectrum ratio of the connection port is 1 or more.

Based on the results of the above examination, the present invention covers the surface of the polymer resin layer with a first layer made of a substance that hardly causes a redeposited layer and does not contaminate the substrate when the sputter cleaning is performed. By making the structure and then performing the sputter cleaning and the formation of the second layer, it is possible to realize a sufficiently low contact resistance even in the connection port portion having an aspect ratio of 1/2 or more. The reason for not using Cr or an alloy or compound containing Cr as the main component for the first layer is as follows. In FIG. 1 (a), the polymer resin layer 21 such as polyimide has an aspect ratio of 1/2.
It is generally known that it is difficult to use a wet chemical etching liquid for forming the connection port 23. As an alternative method, Homma, et al., IE Day M Technical Digest (Homma, et al; IE
DM Tehnical Digest) 1979, p54,
A dry etching method using a mixed gas of O ₂ or O ₂ and a Freon-based gas of Ar and O ₂ is used. However, the first layer 27 is slightly etched by this dry etching method. The etched first layer adheres to the inside of the etching apparatus and the surface of the substrate 20. When the substrate 20 is mainly composed of Si and the first layer is mainly composed of Cr, the deposited Cr is formed there because it is quickly diffused into Si of the substrate 20 at a relatively low temperature (350 ° C. or higher). This is because the characteristics of the element (not shown) that has been formed are impaired. On the surface of the substrate 20 exposed when the connection port 23 is formed, a reaction layer 24 mainly composed of an oxide of a substance forming the surface of the substrate 20 is formed. An etching mask (not shown) made of photoresist is often used to form the pattern of the connection port 23 in the first layer 27. In most cases, this etching mask is a polymer resin layer. 21 Etching is done at the same time. Next, as shown in FIG. 1 (b), the surface of the substrate 20 is subjected to sputter cleaning to remove the first layer 27.
And a part of the reaction layer 24 are removed by etching. Further substrate
The second layer 25 is deposited without exposing 20 to the atmosphere. As shown in FIG. 1 (c), the wiring structure of the present invention is formed by removing the exposed portion of the first layer 27 using the second layer 25 as a mask as needed. If the first layer 27 is not conductive, it is not always necessary to remove the exposed portion.

As the first layer, metals such as Ni, Ti, Mo, Ta, W, Pt, Pd, alloys of these with Al and Cu, and further nitrides such as Al, Ti, Ta, Si and oxides with nitrides A mixture of products is suitable. The second layer is the main component of the conductive path and is preferably Al or Cu or an alloy of these with Si, Be, Ni, Pd, Ti, W, Ta, Mo, etc., but it is not always a single layer. It is not necessary to use a laminated film of the above substances. In the wiring structure of the present invention, the second layer
When the above-mentioned metal, alloy or compound having excellent moisture resistance and heat resistance is used as the first layer 27 under 25, corrosion of the second layer 25 due to moisture in the polymer resin layer 21 is unlikely to occur. Therefore, the reliability of the wiring structure is significantly improved. In addition,
The water content in the polymer resin layer 21 is not originally contained in the resin layer, but is supposed to penetrate into and penetrate the polymer resin layer 21 from the outside and reach the wiring layer. Moreover, it is difficult to reduce the contact resistance between the second layer 25 and the layer (not shown) exposed at the bottom of the connection port 23 to 1 × 10 ⁻⁸ Ω · cm ² or less in the conventional technique. However, when the present invention is used, the polymer resin layer 21 is hardly etched during the cleaning of the sputter, so that as shown in FIG.
Even if the aspect ratio of 23 exceeds 1, before the heat treatment to reduce the resistance, 1 to 3 × 10 ^-9 Ωcm
^It has significant advantages over the prior art, such as low contact resistance of ² (before heat treatment).

Example of Invention

 An embodiment will be described below with reference to FIG.

Example 1 In FIG. 1 (a), a substrate 20 is an integrated circuit substrate on which semiconductor elements (not shown) and the like are formed, and a predetermined portion of an insulating layer (not shown) on the surface thereof is removed. This shows that the connection between the element and the wiring layer is exposed. A polymer resin layer 21 made of a polyimide resin having a thickness of 1 μm is formed thereon by a coating method. A first layer 27 made of a Ti nitrogen compound (TiN) having a thickness of about 50 nm is deposited thereon, and a 1 μm square portion corresponding to a connecting portion between the element and the wiring layer is removed by etching. Using this as a mask, the polymer resin layer 21 was removed by reactive sputtering using O _2, and the reaction layer made of Si oxide was formed on the surface of the connecting portion of the device.
24 shows a state where 24 is generated. The reaction layer 24 is generally said to be 5 to 20 nm although it varies depending on the substance, etching conditions and the like. Next, as shown in FIG. 1 (b), the first layer 27 was etched to 30 nm by a sputter cleaning using Ar. During this etching, the reactant layer 24 was also removed at the same time. Then, as the second layer 25, the thickness is about 0.9 μ.
m Al-2% Si alloy was deposited and processed into a predetermined shape using the photoresist as a mask. Further, the first layer was also processed using the second layer as a mask to form a wiring structure. In this embodiment, the first layer of TiN is formed under the second layer 25.
Since the TiN layer 27 is present and this TiN does not allow water and the like to permeate, it has the effect of preventing the corrosion of the second layer 25.
In the so-called moisture resistance reliability test, the life was improved by about one digit compared to the conventional structure. The second layer is in direct contact with the polymer resin layer 21 inside the connection hole 23, and it can be said that the second layer is more likely to be corroded than other portions. However, the progress of corrosion is local or stochastic, and since the connection area of the connection port 23 is small, practically no problem occurs. In this example, the connection resistance was as low as 1.5 × 10 ⁻⁹ Ω · cm ² .

Example 2 The same substrate 20 and polymer resin layer 21 as those in Example were used. As the first layer 27, Ta was formed by sputtering with a thickness of 60 nm. The portion corresponding to the connection port 23 was removed by reactive sputtering using CF ₄ gas using a photoresist as a mask, and the connection port 23 was formed by the same method as in Example 1. Then, the second layer 25 was deposited under the same conditions as in Example 1 to form a wiring pattern. With this structure, the effect is almost the same as that of the first embodiment,
While the TiN film has to be formed by reactive sputtering or CVD, Ta in this embodiment can be deposited by an ordinary sputtering method, which is a simpler method.

Example 3 In FIG. 1A, a Si wafer including a MOS element and a lower wiring layer (not shown) made of an Al-1% Cu alloy connected to the MOS element was used as the substrate 20. A polyimide resin 21 having a thickness of about 2 μm was deposited thereon, and a 100 nm silica film (SiO ₂ film formed by a coating method) was formed as the first layer 27. The silica film corresponding to 1.5 × 1.5 μm ² in the portion to be connected to the lower wiring layer was removed, and the polymer resin layer 21 was etched in the same manner as in Example 1 to form the connection port 23. A wiring structure was formed by the same procedure as in Example 1 below. In the present embodiment, the first layer 27 is insulative, and it is not always necessary to remove the exposed portion along the second layer 25 after processing the second layer 25. However, the polymer resin layer 21 under the first layer 27 is mechanically soft, while the first layer 27 is mechanically hard and fragile, so that it is damaged when an external mechanical force is applied to it. The exposed portions are removed because the polymer resin layer 21, the second layer 27, and the like may be damaged by debris or the like. The effect of this embodiment is similar to the previous two examples, but it is simpler in that the first layer 27 can be formed by a coating method.

Example 4 Substrate 20 and polymer resin layer 21 in FIG.
Was the same as in Example 3. Then decompress CV on top of this
A 100 nm W film was formed by the D method. The W film was formed by using WF ₅ as a gas source and at a substrate temperature of about 350 ° C. under a pressure of 0.5 to 1 Torr. Next, this W film was etched with a hydrogen peroxide solution. Approximately 30 nm of WC (tungsten carbide layer) generated by the reaction with the polyimide resin during the formation of the W film remained on the surface of the polymer resin layer 21, and this was used as the first layer 27. Then, using the resist as a mask, the 2 μm square WC at the portion where the connection port 23 is to be formed is removed by Ar ion beam,
Hereinafter, a wiring structure similar to that of Example 1 was formed. In this embodiment, Al / Ta / Al is 400 nm / each as the second layer.
A laminated film of 10 nm / 400 nm was used. In this embodiment, it takes some time to form the first layer 27, but since the formed product is a reaction product with the polymer resin layer 21, the polymer resin layer 21 and the second layer 27 are formed. It has the advantage that the adhesion with 25 is very good.

〔The invention's effect〕

As is clear from the above description, the wiring structure and the manufacturing method thereof according to the present invention have the following advantages over the prior art.

1) Even if a connection port with an aspect ratio of 1/2 or more is used, a sufficiently low contact resistance can be obtained, so that the wiring structure can be miniaturized. Contact resistance is 1 to 3 × 10 ^-9 Ω · cm ^2, which is about 1/1 of the conventional value.
Reduced to 0.

2) Since a layer having excellent moisture resistance or heat resistance is interposed between the polymer resin layer and the wiring layer which is the main component of the conductive path, corrosion of the wiring layer from the polymer resin layer / wiring layer interface is suppressed. ,
The moisture resistance reliability is improved by one digit or more as compared with the conventional technique.

[Brief description of drawings]

FIG. 1 is a sectional view showing a wiring structure of the present invention and a manufacturing method thereof, FIG. 2 is a sectional view showing a wiring structure of the prior art and a manufacturing method thereof, and FIG. 3 is one of the features of the present invention. It is a figure for explaining one. 10,20 …… Substrate, 11,21 …… Polymer resin layer, 12 …… Mask, 13,23… Connection port, 14,24 …… Reaction layer, 15,25 …… Second layer to be wiring layer , 16 …… Redeposited layer, 27 …… First layer.

Claims (1)

(57) [Claims] 1. An insulating film made of an organic polymer and Ni, Ti, Mo, Ta, W, Pt, and Ni, Ti on the surface of a semiconductor substrate.
Mo, Ta, W or Pt and Al or Cu alloy and Al,
A step of stacking and forming a first film made of a material selected from the group consisting of Ti, Ta or Si nitrides and oxides, and removing a predetermined portion of the first film and the insulating film. Aspect ratio is 1/2 or more, and the step of forming an opening in which the side surface slope is substantially vertical, and the semiconductor substrate formed on the surface of the semiconductor substrate exposed through the opening, A step of removing the reaction layer composed of an oxide of a substance constituting the surface by sputter cleaning with an inert gas containing no oxygen; and a step of removing the reaction layer from the exposed surface of the semiconductor substrate through a side portion of the insulating film. 1. A method of manufacturing a wiring structure, comprising: a step of forming a second film made of a conductive film extending on the upper surface of the first film; and a step of processing the second film into a predetermined shape. .